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The invasion ecology of Nymphaea mexicana Zucc. (Mexican Water lily) in South Africa

  • Authors: Naidu, Prinavin
  • Date: 2019
  • Subjects: Nymphaea Mexicana zuccarini , Nymphaea , Nymphaea -- Biological control -- South Africa , Water lilies , Nymphaea -- Ecology -- South Africa , Water lilies -- Biological control -- South Africa , Invasive plants -- Biological control -- South Africa , Aquatic weeds -- Biological control -- South Africa , Water lilies -- Ecology -- South Africa
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/92920 , vital:30763
  • Description: The Mexican water lily, Nymphaea mexicana Zuccarini, is an aquatic perennial, native to southern USA and Mexico, and has been introduced to South Africa via the ornamental plant trade. This species has rapid growth rates and becomes weedy in dams, ponds and rivers. It is currently listed as a NEM:BA category 1b invasive plant in South Africa. One possible management measure for this weed is biological control, but it is a novel target because no biological control programme has been initiated against it anywhere in the world. This study is intended as a baseline for the biological control programme against this plant in South Africa. Assessing the population structure and mode of reproduction of invasive alien plants is an imperative aid to determining if biological control is a suitable management option. Using amplified fragment length polymorphism (AFLP) molecular markers, I compared the amount of genetic variability and differentiation of N. mexicana in its native range (USA), and invasive range (South Africa). Results indicated a large genetic distance between populations in the USA and South Africa, compared to populations within each country. The genetic variability of the invasive populations was higher than that found in the native distribution. This could be due to hybridization in the introduced range, and/or multiple introductions from different source populations. Differences in the morphology of N. mexicana plants in the invasive range and South Africa were also observed which confirm the results of the genetic analyses. I also assessed the reproductive mode of N. mexicana cultivars/hybrids by conducting breeding system experiments and field pollinator studies. Results indicated that the cultivars are sterile, suggesting that the primary mode of reproduction is asexual via fragmentation of tubers. The main pollinators that were found to be associated with the cultivars in South Africa were honeybees, sweat bees, flies and beetles. These insect groups were the same as those that were observed in another study which was conducted on the pollinators associated with the pure N. mexicana in the native range in southern USA. Mechanical and chemical control of N. mexicana and its multiple genotypes have been applied but have not been efficient due to the fast regeneration of shoots, especially in summer. Therefore, these two management options are not long–term solutions and will also be costly due to the widespread occurrence of the hybrids in South Africa. Thus the only cost–effective, environmentally friendly, self–sustainable and long–term management option is biological control. The significant divergence between native and invasive populations of N. mexicana, as well as the possibility of numerous invasive cultivars, may limit future prospects of biological control of this species. However the differences in the root structures between native South African waterlilies, such as N. lotus and N. nouchali, and the introduced waterlilies, such as N. mexicana and its associated hybrids, may play a pivotal role in the success of biological control of the N. mexicana hybrid complex in South Africa. Natural enemies which feed on the hard tuberous roots of N. mexicana and its hybrids, as opposed to the soft bulbs of the native N. nouchali and N. lotus, should be prioritised.
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  • Date Issued: 2019

Judging psycholegal reporting in civil court proceedings in the Eastern Cape

  • Authors: Marais, Claire Anne
  • Date: 2018
  • Subjects: Court proceedings -- South Africa -- Eastern Cape , Evidence, Expert -- South Africa -- Eastern Cape , Forensic psychology -- South Africa -- Eastern Cape , Quality Rating Scale (QRS) , Psycholegal reporting -- South Africa -- Eastern Cape
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10962/62999 , vital:28352
  • Description: Purpose: The primary purpose for this research was to evaluate the quality of psycholegal reports, and the qualification of the authors. Previous research had revealed generalised poor practices in psycholegal report writing and the authors seemed unqualified as expert witness. This negatively influenced the impression and usefulness of expert psychological opinion in South African courts. The secondary purpose was to compare the results to those determined by Ireland (2012), which was a useful benchmark study in the UK as her findings corresponded with the literature. Method: This archival research analysed a hand-search sample of 20 reports written by 20 psychologists based nationally. These reports were submitted as expert opinion in civil proceedings in the Grahamstown Division of the Eastern Cape High Court between 2011 and 2016. Ireland and Pinschof’s (2009) measure ‘Quality Rating Scale’ was adapted for a South African context and used to evaluate quantitatively the reports. Focus was on the reports’ contents (fact and opinion), methods, process and overall rating, and the qualification of the authors. Results: Overall, two-thirds of the reports were rated as ‘good’ and ‘very good’. The results were generally more positive than Ireland’s (2012) findings. However, there were practices in the report writing that were deemed detrimental to the quality of the expert’s opinion. This included vague referral questions and unclear basis for concluding opinions and diagnosis. There was also a lack of discussions surrounding the scientific trustworthiness of testing methods and absent ethical considerations. Lastly, the specialised expertise of the experts was not adequately documented. Conclusion: The findings painted a more positive picture of psycholegal reporting in South Africa than illustrated in previous research, which seemingly relied on anecdotes and subjective surveys. This study used a systematic and objective measure. The findings of this study, previous research and ethical Rules of Conduct were used to consider recommendations for psycholegal report writing, and the improvement of the field of psycholegal work. Lastly, the focus of future research was discussed.
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  • Date Issued: 2018

Apparent digestibility coefficients of feed ingredients and essential amino acid requirements of dusky kob (Argyrosomus japonicus)

  • Authors: Adesola, Abidemi Adejoke
  • Date: 2017
  • Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/32140 , vital:24014
  • Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
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  • Date Issued: 2017

The ecological impacts of pollution on a river ecosystem: a community index and stable isotope approach

  • Authors: Gininda, Simphiwe Linah
  • Date: 2017
  • Subjects: Water -- Pollution -- Bloukrans River , Water quality -- South Africa -- Makhanda , Stream ecology -- South Africa -- Makhanda , South African Scoring System , Sewage disposal in rivers, lakes, etc. -- South Africa -- Makhanda , Agricultural ecology -- South Africa -- Makhanda , Agricultural pollution -- South Africa -- Makhanda
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/7993 , vital:21331
  • Description: For decades, urbanized rivers have been modified to meet the needs of constantly expanding human populations in many countries around the world. The Bloukrans River in Grahamstown is one of the polluted and structurally modified urban rivers in South Africa, and there is no published information regarding its water quality and ecological status. Water quality is threatened by human activities including the disposal of treated and raw sewage, livestock farming, and agriculture. This study was conducted to determine the ecological status of the river by assessing its biological, chemical, and physical components in relation to man-mediated activities. Biological responses of macroinvertebrates were used to assess changes in water quality through space and time based on the South African Scoring System version 5 and the Average Score per Taxon water quality indices. The results showed poor water quality due to high nitrate and ammonium concentrations derived from sewage, and channel modifications by agricultural activities and dumping of solid waste. Channel width, water depth, dissolved oxygen, nitrate, and ammonium concentrations were the main drivers of macroinvertebrate distribution patterns and had the most influence on the variability in macroinvertebrates taxa richness, diversity and abundance. Diatoms were also used to assess water quality, specifically to indicate the trophic status of the river based on changes in the Trophic Diatom Index. The results suggested that the Bloukrans River was eutrophic during the course of this study. However, the trophic status varied with freshwater input, resulting in mesotrophic conditions during flooding and eutrophication in dry seasons. Changes in pH, phosphate concentration, water velocity (current speed), and temperature influenced the distribution of diatoms in the Bloukrans River. However, only pH was important at the community level and significantly influenced diatom abundances. Stable nitrogen isotope ratios (S15N) of autotrophs and primary and secondary consumers revealed noticeable differences between tissues of organisms exposed to treated sewage and those without any exposure. The S15N values in biota occurring above the sewage treatment discharge point were low, and those collected below the sewage point were higher. Although fertilizer derived nitrogen is generally depleted in 15N, agriculture-derived nitrogen could not be excluded as a possible source since animals at the sample site that was most affected by agricultural activities had the highest S15N values. This study provided valuable information on the ecological status of the Bloukrans River and identified the major activities associated with reduced biodiversity and water quality.
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  • Date Issued: 2017

The just figure shape, harmony and proportion in a selection of Andrew Marvell's lyrics

  • Authors: Gardner, Corinna
  • Date: 1994
  • Subjects: Marvell, Andrew, 1621-1678 -- Criticism and interpretation , English poetry -- Early modern, 1500-1700 -- History and criticism
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2230 , http://hdl.handle.net/10962/d1002273 , Marvell, Andrew, 1621-1678 -- Criticism and interpretation , English poetry -- Early modern, 1500-1700 -- History and criticism
  • Description: The phrase "the just Figure" - a quotation from Upon Appleton House - is the central theme of this thesis as it aptly describes Marvell's repeated use of shape, harmony and proportion to suggest morality and virtue. The poet's concern with geometrical imagery is conveyed by the word "figure", which also is another term for a metaphor or conceit. The word "just" suggests not only moral appropriateness, but also mathematical exactness or fit. The thesis consists of five chapters, each dealing with an aspect of the imagery of shape and form which pervades so many of Marvell's lyrics. The first chapter, "Moral Geometry", deals with the way in which Marvell uses the imagery of lines, angles and curves. In some poems the lines are curved, as in Upon the Hill and Grove at Bill-borrow, where the graceful downward curved line of the hill conveys Fairfacian humility. Symmetry and circularity are discussed in the second chapter. The poet uses the perfect shape of the circle to depict objects which convey a moral significance. Similarly, several of the lyrics are themselves quasi-circular with their closing lines echoing their openings. Chapter Three deals with liquid spheres. Marvell explores the nature, shape and texture of tears in poems such as Eyes and Tears and Mourning; and in On a Drop of Dew uses the shape of the dew drop to suggest the perfection of the heavenly realm from which it has been parted. In several of the lyrics, Marvell places a frame around his poems to create an enclosed world in which his poetic creations exist. These enclosed, or framed, worlds are discussed in Chapter Four. The final chapter, "Beyond The Frame", describes how some of the lyrics suggest a move from the world within to the world beyond the frame of the poem.This can either be a movement from confinement to release, or from the seen world to worlds unseen. Shape, harmony and proportion are the qualities which Marvell uses to convey morality and humility and a vision of the world based on what is, in the various senses of the word, "just".
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  • Date Issued: 1994
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